Potential Interference with Preconditioning: Animal studies have found that beta-blockers, sulfonylurea, caffeine, aminophylline, angiotensin converting enzyme inhibitors, and naloxone interfere with IPC. Patients on any of these drugs will be excluded. There are studies showing that inhalational anesthetics are pharmacologic preconditioning agents. The mechanism of action involves some of the same pathways as IPC. However, the response to IPC and anesthetic preconditioning involve a substantial subset of genes unique to each preconditioning stimulus. Studies of anesthetic preconditioning have found conflicting results suggesting that anesthetic preconditioning, if it occurs, is likely to be enhanced by IPC. Furthermore, in clinical studies with promising results discussed above, anesthetics were used during the surgical procedure.